This application addresses broad Challenge Area (11) Regenerative Medicine and Specific Challenge Topic, 11-DK-101: Promote regeneration and repair in the digestive system, liver, pancreas, kidneys, Hematologic, and urological system. The stress of major surgical procedures, irradiation, chemotherapy, nutritional deprivation, and systemic inflammation all lead to atrophic changes in the gut epithelium, which significantly affects the outcome of these patients. Restricting dietary intake, a common complication in patients who have undergone severe systematic illness such as trauma and sepsis, leads to intestinal mucosal atrophy and barrier dysfunction, which may result in the migration of intestinal microbes and toxins to the systemic circulation. Thus, regulation of intestinal epithelial growth and regeneration impacts on many problems relevant to a variety of diseases. The central hypothesis of this proposal is that intestinal subepithelial myofibroblasts (ISEMF) play central roles in intestinal epithelial regeneration;induction of certain growth factors by ISEMF may significantly improve intestinal epithelial integrity and function. Our studies will show that the expression of amphiregulin (AREG), a member of the epidermal growth factor (EGF) family, can be strongly induced in ISEMF that stimulates intestinal epithelial regeneration. The essential role of AREG in intestinal regeneration will be demonstrated in our preliminary studies. We will prove our hypothesis that AREG is a critical mediator for Forskolin- and PGE2-induced intestinal regeneration using AREG knockout mouse. In Aim 2, we will show that intestinal subepithelial myofibroblast (ISEMF) is the primary cell type that produces AREG in the intestinal epithelium. Given the special localization of ISEMF in the intestinal mucosa, Aim 3 will elucidate the functional roles of ISEMF in conversion of PGE2 signaling into EGFR activity in intestinal epithelial growth. Finally, we will determine additional compounds which stimulate AREG in ISEMF and may be suitable for clinical use. In conclusion, our studies will provide the evidence that treatments, such as Forskolin and PGE2, which specifically stimulate the production of AREG in ISEMF, represent an innovative therapeutic strategy for improving the integrity and function of the GI tract. PUBLIC HEALTH RELVANCE: The stress of major surgical procedures, trauma, systemic inflammation, and nutritional deprivation, all lead to atrophic changes in the gut, which significantly affects the outcome of these patients. Development of novel treatments to prevent gut atrophy will benefit many critically ill patients. The present project attempts to understand the molecular mechanisms governing intestinal regeneration and develop a novel therapeutic strategy for improving the integrity and function of the gut.